Are you an IC doing tech screens? An EM or Director doing loops like those in the OP? How much feedback have you gotten in the past 2 years about the success (or lack thereof) of the candidates you interviewed, whether you hired them or not? (Here "success" is how they aligned to your evaluation-- could be they had _financial_ success or _career_ success choosing some other job).
EMs will sometimes try to keep tabs on "false negatives," and at the Director / VP Level there's more formal analytical effort (though a lot of it is trying to hit quotas, even if those quotas are bloated or poorly defined). But this aggregate information very rarely bubbles down to the panel and in particular the individuals who interacted with the candidate.
Why keep so many people in the dark? For one thing, if results were disseminated, then salaries / offers would leak too, and then the engineering org becomes much more expensive. (Ironically, the employee stock pool is tiny, and engineering salaries are often not the biggest cost to a Co. The issue here is more about the C-levels having so little understanding of the job market. That's why Steve Jobs wanted a no-poach-- he had no idea what his coveted Safari employees actually did).
Moreover, panels suck. They get stuff wrong all the time. I have never been on a panel that has not moved the goalposts at least 3-4 times between candidates as the panel tries to figure out what the panel even really wants. If ICs and the panel got to know about the outcomes of their actions, they're going to question what happened. And the higher-ups don't want to spend time having that debate.
How can we prevent outcomes like those illustrated in the OP?
If you're a recruiter, stop shotgunning candidates. Try to figure out what your client really wants, and poke half the passives you might otherwise. For actives, give _useful_ feedback, even if it's just verbally. If bombing one leetcode is all it takes relative to the rest of the pool, that can be good for a junior engineer to know.
If you're an IC doing interview loops, do a quarterly review of the candidates you interviewed and the panels you were on. Insist to your manager that you want to do this as part of your 1:1s. Think critically about the loops and discuss with others.
If you're a Director / VP / C-level, stop treating candidates like toys. You earn outsized compensation because you're supposed to be a force multiplier-- you're supposed to assemble an amazing team. If you fell into a goldmine of an opportunity, be extra generous to candidates. You're going to build a good team out of luck, not your own ability, and you'll thank yourself later for not being a sore winner. If your funnel sucks (e.g. you're a tiny unknown start-up), expect to need to improvise, and don't blame candidates for your own bad luck.